Cord circuit



Jan. 29, 1924. 1,482,374 A. J. sEYMQuR CORD CIRCUIT 'oriqin'allmm 1s, 191e 2 sheets-sneer 1 .g b R- [-(Ilh A HF" :llllilh M l fnpefz for,

Ariza/ e mam Patented Jan. 29, 1924.

TELEPHONE M e TION OF NEW YORK.

ANUFACTURING CMPANY, or ROCHESTER, NEW YORK, A CORPORA- conn ciuccia.

Be -llkWl that I, `ARTHR J. SYMR, a'cit'z'en of the United States, residing 'at St;V Pau-l, inthe county 'of Ramsey fand State of Minnesota,"residingat 1938 TerracePaik lArvenu'e,l have invented certain newl an'duseful fmprovements in "Cord v Circuits, of which the following is a specilication.

My invention relates totelephne systems and more particularly `to 'thatfpart of the common battery manually operated/switchboards known to the Vart Vasconinecting cord circuits. p I

In private 1branch enchangefswitchboards l5 "at which a variety ofyl'o'cal "stations and trunk 'lines l'from 'commen"battery"v manually operated "or automatic @exchanges terminate, it is' 'common practice lto equip'theswitchboard 'with diii'e'r'enttypes of cord circuits 2G "with which tojestablish the various coilbinations "of connections. Fordinstanca `a board may comprise-pairs of cords designed for v'setting up j-local to local connections only 5 or pairs of cords `designed for estab- Q5 lisliing `either loc'al 'to loca1,"'l0cal to eX- change, 'orezcchan'geto "ilocal connections. There are also cord 'circuits :termed plug ended, for establishing exchange connec- V tions only. To havea variety `oicord cir- B'cuits onvafswtchboard'is objectionable in that it complicates the process of establishing connections resulting in a lowY 'standard of efficiency, and complicates the switch` Yboard "both from a traiiic 'or maintenance p''iIltf View. l A

The principal jobject of my 'invention' fis to provide improved telephone line connecting means, employing'a'connecting pair of cords terminating in plugs 'offasifnfgle type, and 40 with 'whichufor conversation and signalling, connections 4may be eiected' between two similar or*V tw'o' dissimilar private kbranch eX- chan'ge's'tations, orfbetween either type ot private branch exchange"stations,` (by means ota ltwo-way t'runkfwith acommon (battery manually operated exchange subscriber or with an automatic exchange subscriber; also for cnnectingcither a'lcommon battery eX- l wchange subscriber 'or "automatic 'subscriber 50 by means ofa two ""w'aytrunk with either type of private branch'exchangestation.

A'furthe'r object fof fny invention is to provide, 'in `a 'cord circuitfcertain novel cirn cuit arrangements andl connections whereby `different kinds oflline'sbntriuiks'may 'be Volice connection, causes vLocal to local;

Local to common kbattery manual eX- 60 change;

L'ocal f'to automatic exchange; 1 l"Crlnmmcn battery 'manual exchange =to oca y Automatic exchange to local.

VA` still further Objectis to provide"a 'cord circuit-whereby may be connected any" local station 'with Veither type oflexchanges for incoming or outgoing night, Sunday 'or holiday calls, and wherein the circuit arrangement such thatV theact of replacing the receiver -at 'the local station, after completion of' a conversation on a trunk or central both supervisory lamps 'at thelprivate branch exchange `and 75 thes'upervisorylampatthe central ofiice to light, which is to be lregardedly the operators as `a peremptory "disconnect signal, thereby Vaffording standard through supervision. e y

Referringto the 'accompanying drawings Figure l, shows, diagrammatically, a cord circuit emp'loyingmy invention.

`Figure 2 yisa side elevation of a portion ofthe operators key shelf showing the key levers, plugs and lamps.

Figure Billustrates diagrammatically, an ordinary -prlvate branch exchange circuit showing the"signalling lamp and line'jack forming "part of the usual line terminal `equipment in the switchboard.

-igured shows diagrammatically, 'a well known type of {manualexchange' line circuit anda well known private branchtrunkin connection therewith, showing the trunk jack and lamp forminga part ofthe line terminal equipment in the switchboard.

Figure 5 shows diagrammatically 'a well knwnjautomatic vexchange line circuit in connection with an ordinary private branch `l00 exchange trunk showing the line jack and lamp forming part Aof the line 'terminal equi'pmentin theswitchboard.

Fig." 6 illustrates diagrammatically the calling' `end of the well known VVesternElec- 105 tric cord circuit. A

Before describing, in detaih'the circ-uit operation,"and the switching andthe sig-` nalling features of the "invention, I will `give a brief outline of themode of operation in 11"0 lsupervisory lamp Sfrom to the function o the ack of the station and rings.

At this point the supervisory lamp T of the calling cord isilighted, while the lamp of the `answeririgjfid is 1out. `When the called `station responds, the calling supervisory lamp is extinguished; when the receiver at the called station is replaced upon completion ont the conversatiomboth lamps of applicants cord ycircuit andV the lamp associated with'fthe exchange cord circuit light up as a disconnect signal. The intermittent las`hing of'both lamps as beforeindicates that the operators lattention is wanted.

It is desirable ythat aco'rd circuit be so ar `ranged as to enable the operator receiving the call for an automatic connection, to dial the'called Iparty. ln `order to meet this reuirement applicant has,r provided a dial key connected with the1 usual 'dialling device P diagrammatically indicated inthe drawings.

Operation of cz'rcwlts.4

I of the circuit in the process of'estab'lishingla connectionrfor conversation rbetween `two stations of a` private The operation branch exchange system is as follows:

At the station desiring a connection the receiver is removed `from"the hook switch of the telephone, which lights the usual lamp (F ig. 3) 4forriiing 'part 'of the `line terminal equipment in the switchboard.,V The operator inserts the answering' plug U of an idlevpair in y the lamp and operates relay A, 'ground' from jack I Fig. `3l to lower armature contact'of relayv to windingoi tombattery Ito ground, which in turn connects relayl B acrossrcord` circuit; ring of plug to lo'w'der inner .armature front contact relay ,to lower windingrelay B tobattery'to ground to upper winding B to front contact iiipper armature relay A to tipofycord. This rela-y immediatelyv operates and j prevents the i lighting; thereceiverbein off the hook, 'ground to upper winding re ay to front contact upper armature relay A 'through instrument ,to lower innenarinature 'relay A `it'rht IContact to lower winding B to battery to ground. lt is f relay B to supply current ,to`

the telephone transmitter and to cause the lamp to' light cordlT olffthe pair in theline l. of the station wanted and rings in the usual way.

the' line j aek h l, which puts `,out

up as a disconnect signal when the receiver is` replacech andalso to cause' the lamptoilash in unison with the upward ce The insertion of the plug operates relay G, ground from jack l (lig. 3) to inner lower armature back contactrelay D, 4to winding G to battery to ground, which in turnconnects relay F across the cord circuit and also 'lights lamp `T` rm ground lower outer armature relay G lower armature relay F and through lamp T to battery to ground. h y Y rlhe operator then moves the ringingley lever and connects ringingcurrent tothe line, which actuates the bell of the called station in the ordinary way. Upon 'removal of the receiver in response to the call, relay F becomes energized ;`ground to upper winding relay F to upper armature front` contact relay G through instrument to lower inner armature front contact relay G to lower winding relay F to battery to ground, thereby extinguishing the lamp T, by'breaking lower contact relay 'F. The two stations are :now connected for conversation; the energizing current Ifor the transmitters and relays B and F, which latter `contol the supervisory lamps being supplied from a common source, which maybe either aflocal storage battery as shown, orsup'ply leads extending Afrom the central olicevand terminating-iat the branch exchange.

The'condensersl as shown are 'interposed between the current supply relays B and F Yso as to confine the direct currentv to the individual stations' when relay A'and G are actuated. H y

'Upon completidn 'et' the"eonvers'ationy rellacingfof the receivers relights the supervisoiy lamps, therebygi i l gnaling the operator that the conversation lterminated.

The relays ,A and G remain energized until the operator 'takes down the connections, thereafter the parts are restored to their normal inactive positions. Thus,I the insertion 'of the answering and 'calling plugs find Iground for circuits to energize relays A and' G which areassociated with. and control, circuit controlling means for lir'st connecting current 'supplying sources across the tip and ring strands ofthe cord circuit, for the instruments of the called and calling party and then opening a signaling circuit associated with oneof said current supplying sources, the flow of the current from` said sources andthe opening of said signaling circuit being controlled from the hool switches ofthe respective instruments., The circuit operation in establishing a connection for a private branch exchange station calling for a subscriber connected with a central energy, manual exchange is as follows:

At the station desiring a connection the receiver is removed from the hookswitch of the telephone which lightsfthe usual lamp (Fig. 3) Aforming a part ofthe line terminal equipment in the switchboard. The operator inserts the answering plug U of an idle pair in the line jack l, which extingnishes thc lamp and operates relay A, which in turn connects relay B across the line in the Inanner just described in the foregoing, regarding connections between two private branch exchanges. The function of relay B is to supply current to the telephone transmitter. The operator having obtained the exchange subscribers number inserts the calling plug V into jack J (Fig. ll) connected to a trunk -line from the central energy office thereby becomes energized, effecting the followi nO action; ground to contact armature relay to winding relay D through battery to ground. Relay D now becoming energized opens the circuit through relay A, ground to jack l (Fig. 3) to lower armature relay D to winding relay Alto battery to ground; thus deenergizing relay A which in turn deenergizes relay B by releasing its own upper and lower inncr armature. Thus the current supply from relay B supplying the transmitter from the private branch exchange is cut olf and a current supplying source from central energy otiice simultaneously cut in. At this point in the process of establishing the connection, relays E and D are still energized and no supervisory lamps are lighted, the local station transmitter being now supplied, as described in the foregoing, with current from the central office.

The called party is now connected in the `usual way by the operator at the central energy manual exchange, the connection being thereby completed for conversation. It will be noted that the tip side condenser K of the private branch exchange cord circuit is shunted by relay E, the functions of the latter being, to provide a path (hereinbefore described) for the direct current to the local station transmitter and to control the relays which cut off the local battery source.

- After completion of the conversation, replacing of the receiver-at the local station opens the direct current path at the hookswitch, thereby deenergizing relay E, which in turn causes relay D to deenergize. Beleasing of the lower armature of relay D, reenergizes sleeve relay A grounding one of its armatures, and thereby relighting both supervisory lamps. The circuits of the supervisory lamps may be traced from the ground,

lower armature front contact relay A to lower armature relayB upper armature relay C thence through two paths in multiple, each comprising a supervisory lamp; one of said paths leading through the answering supervisory lamp S` to battery and the otherthrough lower armature back contact of relay G lower armature relay F, calling supervisory lamp T to battery. At the saine time the central office answering supervisory lamp Y 4) likewise lights up as a disconnect signal.

Thus, it will. be noted, that not only the supervisory lamps at the privateY branch exchange are lighted but also the supervisory light at the central energy manual exchange, this result being effected solely by the operation of replacing the receiver by the calling party, thus securing what is known in the art as through supervision.

Relays A and B operate and function precisely as in connection for conversation be tween two stations of a private branch exchange described in the foregoing, but relays F and G remain inactive because no ground is found in the sleeve of jack J. The supervisoryy lamps are therefore controlled solely by the relay A which alone remains energized when the receiver is restored, but becomes deenergized upon removal of the answering plug, whereafter the lights become dark.

The circuit operation in establishing a connection for a private branch exchange station calling for a subscriber connected with an automatic exchange may be de scribed as follows: y Y

The calling proceeds as if fora central energy manual exchange connection, just described. y

The operator having been told that an automatic connection is wanted, inserts the calling cord of the pair into jack J (Fig. 5) connected to a trunk from the automatic exchange. The insertion of the plug connects the calling station with the automatic equipment, and, by reason of a negative battery C (Fig. 5) being on the tip side of the trunk connected with tip of plug V whereby relay E is operated. The operation of the circuit thereafter being identical with that just described in the process of setting up a connection for a private branch exchange and central energy manual exchange subscriber. However` the circuit interruptions, due to the dialing by the local station as hereinbefore referred to in the outline of mode of operation, would permit ordinary relays to follow each impulse, which woulfl intermittently light the supervisory lamps` To prevent this, relay D is made slow acting.

At this point in the process of establishing the connection, relays E and D are still energized and function recisely as described in the .foregoing with respect to the connection between a private branch exchange andy central energy manual exchange.

The circuit operation in the process of establishing a connection `for a subscriber of a common batterymanual exchange station with a private branch exchange station, may be describedv as fo-llows: An operator, atthemanual exchange stationy receiving a call fora station of a priv'ate branch exchange system inserts a calling cord in the jack of the trunk line extendingto the private branch exchange system andi rings in the usual way, which lights the usuallvlamp D Fig. 4) at the private branch exchange.' The operator at- 'the private branch exchange then inserts the plug'of the answering cord of a pair in the jack J., associated withfthe lamp, after which she throws the listening key. The insertion of the plug puts out thecalling lamp D", and the operation of the listening keyl forms a bridged circuit across the ti andring sides (W and X respectively) cfg' the answering cord, as follows: tip side of answering cord., upper armature back contact relay` A Vto make contact listening key'L, to winding relay C, to lower inner armaturelback contactrelay A to ring side-X of answering cord. Thisl bridge, lwhich consists of the winding relay C, extinguishes the calling supervisory lamp P atthe central'otlice and cuts off the ringingl current when the mode of*l ringing is of the machinetype. Thegcurrent from the manual exchange central (o flice'calling cord now energizes relay C forming a locking circuit which lmay be traced from themanual exchange oflice as follows; negative battery a thru manual exchange otlice ring cord relay b. to tip side of trunk, tip of answeriiig4 plug, ringing key contactM `upper armature back contact relay A to upper armature relay D lower armature relay C winding of relay C lower inner armature back contact relay A ringing key contact MA ring oflanswering plug and back over ring side X of lineto tip side offcalling cord at manual exchange oflice to ground.

- The private branch exchangel operator having been informed of the station wanted, inserts the calling plug in the line jack I (Fig. 3) .of the station wanted and operates the'ringing key. The insertion of the plug, by'reason 4of the grounded sleeve l (Fig. 3) energizes relay Gr which lights the supervisory lamp T (the upper armature relay (l being operated prevents lamp S from operating) the line as` hereinbefore described. When the receiver is taken down from the hookswitch inresponse to the call, relay "F becomes energized. The attraction of its lower armature extinguishes the supervisory lamp T and the'attraction of its upper armature formsY a circuit: thru relay E as follows:

'ground upper armature relay F winding relay -E upper armature relay back` cgntact relay A to break contact ringing key tip side of plug to tip side of-lin'e thru 'central oilice sleeve cord relay Z2 to battery, which `in tulrnsoperates and closes a local circuitof which relay D forms"` a part.

The operation of relay D releases, by attracting its inner lower and'itfs 'upper armature, the4 sleeve relay G and the Arelay C, thereby breaking the locking circuit. The release of relay G' deenergizes relay F which prepares the circuit for relighting of the supervisory lamps. It also bridges the series relay acrossthetip sideicondenser K.

At this point the process ofestablishing the connection, relaysE and D;"alouev are in energized condition. The' former is in thepath thru which direct currentflows from the central office to the called station transmitters the latter (by means of its upper armature) prevents the vbridgingy ofA t'he'winding of relay C across the line when the operator moves her li'steningkey during the Vconversatlon. f

Upon'completion ofthe conversation the act of replacing the receiver at the called,...

The circuit operation in establishing a,

awaits a response from the ollerator,` The usual lamp forming a part of" the trunk terminal' :equipment lights up shortly after the idialing ofthe last ligure, which attracts the` operator7s attention. Thejoperator inserts the answering plug intofthetrunk jack J (Fig. 5) which extinguishes the lamp, and/then throws the listening key and ascer- 'tains'whfat station is wanted.` The operation of the listening key forms a bridgedl circuit across the tip` andring sides of 'the answering cord, which cuts olfthe ringing current.

Having obtained; the information, the -operator insertsthe calling plug V inthe line jack I of the called stationv (Fig. 3)' and rings. At this point ofthe connection relays C and Gr alone arein ,operated'condition. The winding of the i'orrnery is bridged across 'the two sides of the line thru the listening key L contacts, while the latter is energized becausefof-Il the circuit having been formed from the grounded sleeve of the j ack I, thru Vits winding, armature and break contact of relay to battery.- The` energization of this relay lights the calling'supervisory lamp T, ground vto4 front contact lower armature relay Glto lower armature back contact relay F thru 'lamp to battery to ground, andconnects relay F across the line. When at the called station .the receiver is removed to answer the call relay F becomes energized, which extinguishes the supervisory lam by attracting its lower armature, and c oses a circuit by attracting its upper armature, said circuit actuating relay E. This circuit may| be traced from ground, upper armature front contact relay F to relay E, and upper armature relay A, tip side of line to negative battery at the automatic exchange connector. The operation of relay E closes a local circuit of which relay D forms a part, the energization of the latter breaking by means of its upper armature the locking circuit of relay C and also deenergizing relay Gr.

The breaking of the locking circuit removes the bridge from the line and the deenergization of relay G disconnects relay F from the line and` connects series relay E in shunt around the tip side condenser. Relay E is now kept in operated condition by current fed from the automatic exchange. As described in the foregoing in the connection between a private branch exchange and subscriber connec'ted with a central energy manual exchange station, upon completion of the conversation the act of replacing the receiver at the called station causes both supervisoify lamps to light up. To accommodate incoming and outgoing calls on Sundays or holidays `or when the private branch exchange operator is absent a cut out key Z is provided to disconnect battery. The circuit operation may be described as follows from 'tip side of lug to upper armature relay A thru relay E to upper armature relay G to tip of plug and from ring lower inner armature relay A to lower inner armature relay G to ring of plu The operator simply leaves the calling and answering plugs inserted until her return, incoming and outgoing calls passing thru the private branch exchange cord circuit to the central office where the connections are effected in the usual way, thereby eliminating the use of plain cords usually used foi` this purpose. The conductors L of 'the listening` key L lead tothe operators set.

I claim:

l. In a telephone system, the combination withcalled and calling subscribers lines, a central exchange in connection with certain of said lines and a current source at said exchange; of acord circuit including calling and answering plugs for interconnecting said lines, a current supply, means including a circuit responsive to connection of said answering plug with a subscribers line for connecting said current supply across said ycord circuit and means in said cord circuit operated by the connection of said calling plug with a certain one of said lines for simultaneously cutting off the current supply acrossdsaidy Icord circuit and cutting in the current source from said central exchange.

2. In a telephone system, the combination with called and calling lines, a called line extending through an automatic central exchange, and a current supply at the exchange bridged across said called line; of a cord conductor between thel a shuntV path about saidv condenser and disconnecting said current source from said cord circuit.

3. In a telephone system, the combination with the called and callinglines and their instruments, an automatic central exchange. a trunk terminating thereat, the called line having connection with said automatic central exchange trunk and a current source associated with the called line at said central exchange; of a cord circuit comprising tip and ring conductors terminating at their respective ends in plugs to interconnect said trunk and calling line, a current supply, a feed relay connected with said current supply, sleeve relays having armatures, controlling circuits for said sleeve relays, certain of said armatures serving to bridge said feed relay across said tip and ring conductors responsive to the engagement of the answering plug with the calling line, a condenser in the tip conductor, a seriesrelay connected to the tip conductor about said condenser and operated through the calling plug by said current source at the central exchange, a local circuit including a slow acting relay, an armature associated with said series relay to close said local circuit, said slow acting relay functioning to break said sleeve relay circuits, supervisory lamps, and4 circuits therefor including armatures associated with said sleeve and feed relays.

` 4:. In a telephone system, the combination with an exchange, a subscribers telephone line and a trunk connected thereto, other telephone lines serving as calling and called lines, telephone instruments including receivers and switch hooks for said lines, jacks of the called line and calling lines, signaling means and a current source at the exchange, the jacks of certain of the subscribers line circuit-s having said current source connected thereto; of a cord circuit comprising tip and ring conductors, an answering plugl and a calling plug for said conductors to connect the telephone lines through said exchange and trunk, a listening key associated with said tip andring conductors,l a-relay associated with said conductors and. said listening key, said relay arranged to be bridgedA across theanswering end of the cord circuit on actuation of said key to connect said relay With said exchange over said trunk, supervisory lamps, normally open circuits for said lamps, means including a circuit controlled by connection ofthe calling plug With the called line, said means being operated by the called line circuit for lirst operating one otfsaid super visory lamps, then rendering and holding the latter inoperative and breaking said relay bridge to cut out said current source, and means operated by said last-named means responsive to the replacing of the receivers on their respective hookswitches for rendering said exchange signaling meansl and cord circuit lamps effective.

` y. In a, private branch exchange system having. connection with local stations and with trunk lines `from a central energyv manually operated switchboard and lines fromV an automatic exchange with theline circuits ccntrolledby the subscribers; of a cord,E circuit comprising a calling and answering cord for inter-connecting local stationsV or a local station and any ot said lines, a' listening key in connection with said cord circuit, plugs for each cord, primaryI andl secondary signaling means, current sources, means for connecting said signaling means to said current source with said local),y station linesA andoperating said primary signaling means, and auxiliary meanscontrolled by actuation ot'saidlistenias key and allsuernslplue felt Qperatms saidy secondary signaling means. i

6. In` a teleplicne systemincludingrsubscriberfcontrclled lines local lines and trunk lines, telephones including receivers and n hook-switches for, certain ot said5 lines, a

manually operated central exchange having a current source connected tocertain of said lines, an operators listening key, a cord circuity comprising tip and ring' conductors, a plug. at each end thereof, interrelated; relays. associated with said tip and ring conductors, certain of saidV relays being1 arranged to 'form tWo groups, a normally open local relay, circuit in each` group connected with al current source and with tip and ring conductors, each of said circuits4 arranged to `be associated with a local station through said plugs,` normally open lamp circuits, supervisory lamps in said circuits common to all the said line connections tofbe operated by said lamp circuits when they are' closed, said relay'and lamp circuits being operated by connection. of the cord circuit with said local stations, said current source circuitsbeing closed when therespective receivers of the connected lines are ott their respective hook-switches, means responsive to manipulation of said plugs to effect connections between a called line ot a local station and a calling line connected With a manually operated central exchange said means comprisinga locking circuit to bridge said tip and ring conductors and adapted on closing to connect into said circuit said exchange current source by operation of said listening key, a relay in said locking circuit to hold open one otsaid norw mally open circuits, and a third group of relays associated with oneo said groups of yrelays of said cord circuit and rendered operative by the latter to break said locking circuit when the line circuit is closed, one ot Vthe first named group of relays holding open a normally open circuit, the latter being closed responsive to they breaking of the line circuit by the called subscriber.

7. In a telephone system comprising calledV and calling subscribers lines, a listeningkey, local station lines, trunk lines from a centralenergy manual exchange and trunk lines from an automatic exchange, a cord circuit including a tip and a. ring conductor and a calling and an answering plug to inter-connect subscribers lines or subscribers7 lines with trunk lines, a normally open supervisory circuit, current supply connections tor the answering and calling sides ot the cord circuit, means effective responsive to connection of the cord circuit with certain ot said lines tor closing saidy supervisoryv circuit and. connecting said` current supply across said tip and ring conductors alv the calling and answering sides of the cord circuit, a condenser in series in each of said tip and ring conductors between said current supply` connections, and means associated with saidl last named meansl for shunting said tip and ring conductors around said condensers on the connection of said cord circuit With other lines.

8,. ln a telephone system, local telephone stations, trunk lines, a central. exchange, distant. telephone stations connc `3tablel with said trunk lines at said exchange, a listenA ing key, a cord circuit comprising a tip and a ring conductor, a contact plug at each end thereof, series condenscrs in the tip and; ring conductors. relays, armatures therefor, a shunt about the condenser in the tip conductor including certain ot said armatures, a shunt including certain of said armatures about the condenser in the ring conductor, means including a local circuit for each. end ot-thc cord circuit associated with Said plugs and said armatures tor `eft'ecting a talking connection between two loca-l stations, means associated with. the local circuit at the calling end of said cord circuit and certain ot said arma-tures and listening key to ciicct a talking connection between local station and a distant telephone station, and means for holding open nus said'local circuits to render all of the named means inoperative during said last-mentioned telephone connection..

9. In a telephone system, primary and secondary exchanges, telephone lines terminating at each exchange, trunk lines extending between said exchanges, a cord circuit at the primary exchange terminating at each end in plug contacts and having its ends inductively connected but conductively separated from each other, a source oit' current at said primary exchange, a relay at each end of said cord circuit through which said source of current may be connected to each end ot said cord circuit, a second relay associated with each oi said first relays, said second relay being operated by the connection of its associated plug, contacts With a telephone line to connect one; of said first relays and a source of current to the telephone lines through said cord circuit, a supply of current at said second exchange, means operative responsive to the connection ct said cord circuit with said trunk for conductively connecting` the ends of' said cord circuit and extending said cord circuitfover a trunk line to the supply of current at said second exchange, and means effective to disable said second relays of the cord circuit on the connection of said cord circuit to said trunk line.

secondary exchanges, telephone lines terminating in each exchange, trunk lines extending between said exchanges, means for connecting a telephone line at one exchange With a trunk line, a cord circuit at said second exchange for interconnecting telephone lines terminating thereat or for interconnecting one of said telephone lines with one of said trunk lines, said cord circuit including tip and ring conductors, the ends of each conductor being inductively 4connected but conductively separated, a

sleeve conductor for each end ot' said cord circuit, a sleeve relay normally connected to each sleeve conductor a source of current at Said second exchange, a current feed relay, a circuit extending from said source of current through the Winding of said current feed relay and a contact of the sleeve relay to one of the conductors of said cord circuit, a supply of current at said first mentioned office, and means responsive to the connection of said cord circuit with said Erst mentioned exchange over a trunk line for disconnecting said current Jfeed relay from said cord circuit conductor and for lextending thereto a supply of current at necting a telephone line at the primary office to one of said trunk lines leading to said secondary office, a source of transmitter current at said primary office, a cord circuit for interconnecting said trunk line at one end tcsaid telephone lines terminating at said secondary oiiice, the ends of said cord circuit being inductively connected together but conductively separated Jfrom each other, a'source of transmitter current at said sec ondary office, means including a current feed relay associa-ted with cach end of said cord circuitl through which said last mentioned source of' transmitter current is connected to the respective ends of said cord circuit, a second relay for each end of said cord circuit controlling the connection of said last mentioned source ot current to the ends of said cord circuit, and inea-ns controlled at one of said second relays for disconnecting said second source of transmitter current and for connecting saidlfirst source of' transmitter current to both ends ot said cord circuit.

12. In a telephone system, a primary exchange, a secondary exchange, trunk lines for interconnecting said exchanges, telephone lines terminating at each exchange, a transmitter for each telephoney line, means for connecting a telephone line at the primary Voiiice to one of said trunk lines leading to l0. -In a telephone system, primary and said secondary ofHce, a source of transmitter current at said primary office, a cord circuit for interconnecting said trunlr line and one of said telephone lines terminating at said secondary oiiice, said cord circuit having a plurality of conductors, the ends of said cord circuit being inductively connectedvtogether but conductively separated from each other, a source of transmitter current at said secondary office and means including a current feed relay associated with each end of said cord circuit through which said last mentioned source oi transmitter current is connected to the respective ends ot' said cord circuit, a second relay for each end of said cord circuit controlling the connection of said last mentioned source of current to the ends ot said cord circuit, and a relay serially included in one ot said conductors and controlled at one of said second relays for governing the disconnection of said second source of transmitter current and for connecting said first source of transmitter current to both ends of said cord circuit.

13. In a telephone system, a primary exchange and a secondary exchange, trunk lines extending between said primary and said secondary exchanges, telephone lines terminatingat each of said exchanges means for interconnecting a telephone line at one exchange with a telephone line terminating at a second exchange including one of said trunk lines and a cordV circuit at said secondary exchange, a signal at said primary exchange for indicating the condition of said connection, a sleeve relay for each end of said cord circuit, a source of transmitting current at said secondary exchange, a current feed relay connected to said last mentioned current, said sleeve relays functioning to connect said last mentioned current to both ends of said cord circuit through a current feed relay, supervisory lamps associated with each end of said cord circuit for indicating the condition of said cord circuit, means for operating said signal and said supervisory lamps at the termination of a connection, said last mentioned means including a circuit controlled at the sleeve and current feed relays associated with each end of the cord circuit, and means controlled from the primary office for governing said sleeve relays.

lll. ln a telephone system, a primary exchange, a secondary exchange, trunk lines for interconnecting said exchanges, telephone lines terminating at each exchange, each telephone line including a transmitter, means for connecting a telephone line at the primary oiiice to one of said trunk lines leading to said secondary oce, a source of transmitter current at said primary office, a cord circuit for interconnecting said trunk line and one of said telephone lines terminating at said secondary office, said cord circuit having a plurality of conductors, the ends of said cord circuit being inductively connected together but conductively separated from each other, a source of transmitter current at said secondary office, means including a current feed relay associated with each end of said cord circuit through which said mentioned source of transmitter current is connected to the ends of said cord circuit, a sleeve relay for each end of said cord circuit controlling the connection of said last mentioned source of current to the ends of said cord circuit, a relay serially included in one of said conductors through contacts of one of said current feed relays and one of said sleeve relays, and a slow relay governed by said last mentioned relay, said slow relay effecting the disconnection of said second source of transmitter current and for connecting said first source of trans.- mitter current to both ends of said cord circuit.

l5, ln a telephone system, a primary exchange, a secondary exchange, trunk lines interconnecting said exchanges, telephone lines terminating at each exchange, each telephone line including a transmitter, means for connecting a telephone line at the primary oliice to one of said trunk lines leading to said secondary oiiice, a source of transmitter current at said primary office, a cord circuit for interconnecting said trunk line and one of said telephone lines terminating at said secondary oliice, said cord circuit having a plurality of conductors, the ends of said cord circuit being inductively connected together but conductively separated from each other, a source of transmitter current at said secondary office and means including a current feed relay associated with each end of said cord circuit through which said mentioned source of transmitter current is connected to the ends of said cord circuit, a sleeve relay for each end of said cord circuit controlling the connection of said lost mentioned source of current to the ends of said cord circuit, a supervisory lamp for said cord circuit controlled by one of said current feed relays, a relay serially included in one of said conductors through contacts of one of said current-feed relays, and a slow relay governed by said last mentioned relay, said slow relay eifecting the disconnection of said second source of transmitter current and for connecting said iirst source of transmitter current to both ends of said cord circuit.

16. In a telephone system, a primary exchange, a source of transmitter current at said exchange, a secondary exchange, trunk lines extending between said primary and said secondary exchanges, telephone lines terminating at each of said exchanges, means for interconnecting a telephone line at one exchange with a telephone line terminating at a secondary exchange including one of said trunk lines and a cord circuit at said secondary exchange, a signal at said primary exchange for indicating the condition of said connection, a sleeve relay for each end of said cord circuit, a source of transmitter current at said secondary exchange, current feed relays one connected to said last mentioned source of current and to each end of the cord circuit through contacts of a sleeve relay, supervisory lamps associated with each end of said cord circuit for indicating the condition of said cord circuits, circuits for operating said lamps under the control of the telephone lines, one of said circuits extending through the front contacts of one of said sleeve relays and through the back contacts of a current feed relay, and a slow relay controllable from the primary exchange, a circuit for the other supervisory lamp extending through the back contacts of the other current feed relay and through the front contacts of said other sleeve relay, and circuits for said sleeve relays, completed at the baclr contacts of said slow relay.

In testimony whereof I ax my signature in presence of a witness.

ARTHUR J. SEYMOUR. 

